Method for coating wood and products thereof



Aug. 27, 1957 H. c. KELLY ET AL METHOD F OR COATING WOOD AND PRODUCTSTHEREOF INV EN TORS. Hero/d 6, Ke// By Daniel .Smick United StatesPatent 9 METHOD FOR COATING WOOD AND PRODUCTS THEREOF Harold C. Kellyand Daniel Smick, Midland, Mich, as-

signors to The Dow Chemical Company, Midiand, Mich., a corporation ofDelaware Application February 8, 1956, Serial No. 564,185

13 Claims. (Cl. 117-73) This invention relates to a method for coatingwooden surfaces and articles to protect them against damage from impactand deterioration. More particularly, this invention relates to a methodfor providing wood with a tough and effective protective covering byutilizing a tightlyadhering multicomponent coating system whichcomprises ethyl cellulose. The invention has specific reference to amethod for protectively coating wooden implements and otherparaphernalia employed in various athletic and recreational pursuits andsporting contests, such as baseball bats and bowling pins, whichfrequently are subjected to severe concussive impact. It is alsoconcerned with the sundry coated wooden products which advantageouslyare obtainable with improved physical attributes by the practice of thecoating method.

As is well known, wooden surfaces are propense to I portment is anextremely vundesirable and defective characteristic of wood. Among theseveral serious consequences for which it is responsible is oftentimesan abbreviated useful life span for many articles and implements ofwood.

Baseball bats, for example, are commonly victim to a very high incidenceof breakage in use. Their breakage may be induced by the impact which isoccasioned whenever a baseball is hit by a batsman during the strike ofthe bat, especially if the angle of incidence at which the ball contactsthe bat is not squarely or sufficiently parallel with or edgewise to thegrain to utilize its natural optimum strength or if the locus of contactis too remote from the center of percussion of the bat, as when the ballimpinges on or near the handle or tapered grip portion of the bat. Itmay also occur as the result of casting the bat upon the ground orotherwise causing it to be jarred. Besides actual fractureorsplinter-ing, bat breakage compreheuds other conditions rendering thebat useless or unsatisfactory for additional employment. This includeschecking, pitting, denting, chipping, grain separation and the like.

The breakage of baseball bats entails considerable expense by way ofreplacement on behalf of participants and sponsors of the sport.Furthermore, baseball bats are ordinarily manufactured from betterquality grades of such types of wood as ash or hickory which arebecoming increasingly scarce materials amongthe Nations availableresources and whose conservation is a matter of great practical concern.In addition, the breakage in use of baseball bats is a known proximatecause of injury to both competitors in and spectators of exhibitions ofthe sport.

2,804,399 Patented Aug. 27, 1Q57 While attempts have been made toproduce baseball bats having greater strength and a reducedsusceptibility for breakage, completely satisfactory results have notbeen realized. As an illustration, baseball bats having a laminatedconstruction are usually heavier than is desirable and despite theirgreater strength, have not enjoyed a widespread popularity. They alsoare unattractive in that their cost is excessive in comparison toconventional bats.

Analogous annotation is applicable to such wooden articles as bowlingpins and alleys, polo'and croquet mallets, hockey sticks, cricket bats,arrows and javelins, tool handles, wooden propellors and fans, skis,toboggans, boat hullsand other like and related wooden surfaces andarticles which are subject to damaging impact and other abusiveconditions. It would be advantageous for reasons of economy,conservation and safety to achieve an improved and superior resistanceto breakage and damage for such articles.

It is an object of the present invention to provide a tough, dense,impact-absorbing and shock-cushioning coating for wooden surfaces andarticles to imbue them with superior resistance to breakage and withminimized propensity for physical deterioration under abusive conditionsof employment. It is a further object to provide a coating for woodhaving, in addition to such desiderata, a tightly and tenaciouslyadhering nature. It is a related objective for the coating to beeconomical and procurable from readily obtainable and relativelyinexpensive materials. It is a particular object of the invention toprovide such a salutary coating for various wooden sports andrecreational equipment and apparatus including baseball bats and bowlingpins and to secure greater endurance and extended useful life spans forsuch equipment. It is an additional object to provide a coating of thisnature without detracting from or altering the normally acceptableutilitarian features and indicia of the coated wooden surfaces andarticles. Various other objects and advantages of the invention areapparent throughout the following description and specification.

According to the invention, wooden surfaces and articles mayadvantageously be protectively covered with a multicomponent coatingsystem which comprises first applying at least one priming layer andpreferably more of a polyvinyl acetate latex to the bare surface of thewood; then applying at least one intermediate layer of a nitrocellulosecoating composition over the applied priming layer of polyvinyl acetatelatex; and subsequently applying at least one enveloping layer of anethyl cellu lose coating composition over the applied intermediatenitrocellulose layer. Each of the layers of the multicomponent coatingmay be applied by any suitable technique, including brushing, sprayingor dipping. How ever, whenever it may be feasible, it is usuallyadvantageous for the subsequent ethyl cellulose layer to be derived bydip coating in a gel lacquer formulation. Each applied layer ispreferably permitted to dry thoroughly before application is made of thesucceeding layer. Coated wooden surfaces and articles according to theinvention have a composite, multicomponent, impactresisting andshock-cushioning protective coating comprised of superimposed envelopinglayers of polyvinyl acetate, nitrocellulose and ethyl cellulose. Suchsurfaces and articles have a greatly enhanced resistance to breakage andare less susceptible to damage or deterioration than when they are in anuncoated state.

Most good, commercially-available grades of polyvinyl acetate latex maybe utilized for the priming layer or layers on the wooden surfaces orarticles to be coated. It is convenient to employ the latex in theliquid form in which it is conventionally obtainable. Brush applicationis ordinarily suitable for the latex. As is a customary reforformulation of the gel lacquer.

quirement for the application of most coating materials, the surfaceshould be dry, cleanand free from grease, dirt, fingerprints or dust inorder to obtain the most satisfactory results It is usually advantageousto apply two or three coats of the polyvinyl acetate latex over thebarewoodensurface to insure its thorough priming.

The intermediate nitrocellulose layer may similarly vantageously,however, an alkyd type. resin composition which may be similar to thosewhich are available under the trade-names Paraplex RG-2 and Glyptal 2557from Rohm and Haas Company and General Electric Company, respectively,or a hydrocarbon resin such as the poly alpha methyl styrene having aviscosity of about be obtained from various commercially-available typesof 1 neighborhood of about 70 percent by weight of the weight of thedissolved solids. The nitrocellulose resin may, for example, have aviscosity of 25-35 seconds, as determined by a standard falling ballmethod in a tube which is essentially similar to ASTM Test No. D30l-33.Brush applications of the nitrocellulose lacquer also are usuallysuitable in most instances. The polyvinyl acetate and nitrocelluloselayers provide good anchorage and suitable 1conditions of receptivityfor the subsequent ethyl cellulose ayer.

For most -wooden articles the subsequent impactabsorbing layer mayfrequently be most advantageously derived from an ethyl cellulose gellacquer composition which is applied by means of dip coating over theintermediate nitrocellulose layer. An ethyl cellulose gel lacquer, as isconventionally understood, is a formulation that is particularly adaptedfor hot dip application in order to obtain relatively thick coatingswith minimum application eifort. Frequently a coating having a 5 to 20mil and greater thickness can be obtained readily from a single dip ofthe relatively cooler article in the hot gel lacquer composition. Thegel lacquer may advantageously be formulated with an ethyl cellulosehaving an ethoxyl content, usually-designated medium, in the range fromabout 45 to about 46.5 percent by weight which contains an average ofbetween about 2.25 and 2.35 etherified ethyl substituents per glucoseunit; It may have a viscosity between about and 200 centipoises, asdetermined in a solution of about 5 percent by weight of the ethylcellulose in a solvent mixture consisting of about 80 parts by volume oftoluene and about parts by volume of ethanol. It is frequentlybeneficial to employ a cellulose ether having a viscosity between about50 and 100 centipoises. If desired, light stabilizers and the like canbe incorporated in the cellulose ether to inhibt its discoloration onexposure to light and weathering.

Ethyl cellulose gel lacquers can be prepared with a variety of knownsolvents for dissolving the cellulose ether at an elevated temperature.Beneficially, however, the medium grade of ethyl cellulose gel lacquerswhich are advantageously employed in the practice of the presentinvention may be prepared with a solvent mixture of about 50 to 60 partsby weight of Xylene; about 15 to parts by weight of an aliphaticpetroleum hydrocarbon fraction similar to that which is available underthe trade-designation Apco Thinner from the Anderson Prichard OilCorporation; and about 20 to parts by weight of an ethylene glycol ethylether similar to that which is available under the trade-designationDowanol .8 from The Dow Chemical Company, or that which is known asCellosolve and is obtainable from Carbide and Carbon Chemicals Company.Solvents or solvent mixtures having equivalent solvent power for ethylcellulose and which are commensurate in other characteristics may, ofcourse, also be utilized.

It is frequently desirable to plasticize the ethyl cellulose A varietyof known plasticizers and resins are available for this purpose. Ads

so as to overcome the 900 centipoises at 60 C. which is available underthe trade-designation Dow Resin 276-V9 from The Dow Chemical Company,may be employed. Ordinarily, it is advantageous to employ'not morethanSO percent by weight of the plasticizer, based on the total weightof the plasticized ethyl cellulose. The gel lacquers can be preparedwith varying dissolved solids contents (which includes the weight of theethyl cellulose and the plasticizer). While a dissolved solids contentin the neighborhood of 20-30 percent by weight is normally suitable, itcan be varied over wide limits within and without the mentionedrangeQdepending on the coating thickness which is desired to be obtainedin each dipping operation and the number of dips to be employed. Usuallyit is desirable for the complete application of the gel lacquer to beaccomplishedin one or two dipping operations.

' Ethyl cellulose gel lacquers are best formulated to provide smoothsolutions at sufliciently low temperatures (which, however, are wellabove room temperatures) to minimize solvent lossby evaporation. Thesolvent compositon and its employed concentration should be ca pableofetfecting gelation at a temperature which is about.

20-25 centigrade degrees beneath the dipping temperature. The gellacquers employed in the present invention may be prepared convenientlyby dissolving the ethyl cellulose and plasticizer with suitableagitation in the solvent mixture at a temperature of about 100 C. Afterthe gel lacquer solutionhas been prepared and deaerated, it may beemployed for dip application of the subsequent ethyl cellulose layer inthe composite coating at temperatures between about and C.

If desired, the ethyl cellulose gel lacquers maybe prepared withcellulose ethers which have higher or lower ethoxyl contents than mediumethoxyl grades of ethyl celluloseprovided that suitable adjustment ismade in the solvent system employed. In addition, or alternatively, theethyl cellulose layer on the coated article may be derived from othertypes of ethyl cellulose coating compositions such as conventional ethylcellulose lacquers. In such'cases several applications may be requiredin order to attain a layer of desirable thickness. For many purposes,such as the coating of sizeable wooden surfaces on which dip applicationis impracticable, the brush application of a conventional ethylcellulose lacquer may providea preferable technique for obtaining asuitable ethyl cellulose layer over the applied layers of polyvinylacetate and nitrocellulose.

Usually an ethyl cellulose layer havinga thickness of at least about 5mils and, preferably, between about 15 and 50 mils is applied asthersubsequent layer to'the polyvinyl acetate and nitrocellulose layersin the practice of the present invention. Such a layer has sufiicientthickness to permitthe tough, dense, impact-absorbing and'shock-cushioning properties of the ethyl cellulose portion of themulticomponent coating to protect the Wooden surface or articleefiectively from damage due to shock and impact. It also serves toprotect the wood from other deteriorating influences by providing ampleimpermeability as a barrier against moisture transmission effects ofdehydration and absorption.

While many variations may be suitable in the relative ,Weightproportions of-the layers in the multicomponent 70.

coating of the invention, it is frequently beneficial, especially onsuch wooden articles as baseball bats, for the I relative proportions ofthe superimposed polyvinyl acetate latexznitrocellulosezethyl celluloselayers covering any given area to be roughly in the ratio of 5:1:10 25or thereabout, respectively, on a dry-weight basis. In cer tain articlessuch as baseball bats and bowling pins, where a particular totalweightmust be adhered to, it may be desirable to peel or remove some ofthe wood from the surface of the article or to coat articles which arepurposely undersized so that the weight of the coated article can nearlyapproximate an acceptable weight which is conventional or normal for theparticular article.

The accompanying drawing illustrates several articles which areadvantageously protectively coated'in accordance with the presentinvention. A coated wooden surface, greatly exaggerated out of trueproportion, is represented by a fragmentary sectional view in Figure 1.A baseball bat is perspectively illustrated in Figure 2 and a bowlingpin, broken out partly in section, is shown in Figure 3. A fragmentary,magnified cross-sectional view of the coating layers applied on thebowling pin is shown in Figure 4. i

The composite protective coating, represented generally by the referencenumeral 5, on the surface of the wooden article 4 in Figure 1 iscomprised of a priming layer 6 of polyvinyl acetate latex which servesboth to seal the wood so that bubbling is not caused in the subsequentlyapplied ethyl cellulose layer and to eifect superior adhesion of thecomposite coating 5 on the article. The composite coating 5 alsocomprises an intermediate layer 7 of nitrocellulose, which insures aneffective sealing of the wooden article and provides a bonding meansbetween the polyvinyl acetate layer 6 and the relatively thick,subsequent impact-resisting layer 8 of ethyl cellulose. As mentioned,the polyvinyl acetate layer 6 and the nitrocellulose layer 7 mayadvantageously be brushed on while the ethyl cellulose layer 8 of thecomposite coating 5 may advantageously be derived in suitable thicknessby one or two dip applications with an ethyl cellulose gel lacquercomposition.

A wooden item of sports equipment, such as the baseball hat 9 depictedin Figure 2 may advantageously be provided with such an impact-resistingand shockcushioning composite protective coating 5. Since-the ethylcellulose layer 8 is relatively slippery it may be desirable to providea less slippery or friction gripping surface 10 on such articles asbaseball bats; The friction gripping surface'10 may readily be obtainedwith a coatin of a suitable friction-providing vinyl or neoprenebasedcomposition such as a paint which may be similar to that obtainableunder the trade-designation 1143 Neoprene Gray from the Saran ProtectiveCoating Company of Ferndale, Michigan.

In an analogous manner, it maybe desirable to provide a relatively hard,scratchand dirt stain resisting outer covering or top coat over theethyl cellulose layer of the composite coating in order to reduce thescratching and dirt pickup which may occur directly onthe ethylcellulose layer. This may conveniently be accomplished by application ofa thin covering of a'hard lacquer or like coating material such as thenitrocellulose lacquer and equivalent materials which are conventionallyapplied for such purposes on bowling pins. This is illustrated by thebowling pin 11 shown in Figure 3 on which a composite coating 5 isapplied in accordance with the present invention. The composite coating5, as is illustrated in greater detail by the magnified fragmentarycross-sectional view of the coating on the bowling pin in Figure 4, issuperficially covered by a thin coating 12 of aconventionally-obtainable, light, hard-finish lacquer for purposes ofminimizing scratching and soiling of the protectively coated article.

In a series of illustrative examples which further illustrate thepractice of the invention, sixty (60) ash baseball bats, obtained in anuncoated condition from the Hanna Bat Company of Athens, Georgia, wereprovided with a composite coating consisting of superimposed layers ofpolyvinyl acetate latex, nitrocellulose and ethyl cellulose. Forty-eight(48) of the bats were adapted for use in contests between juvenilecompetitors playing on organized teams'suchas those which participateunder the auspices of the Little League, Inc. Twelve (12) of the batswere regular models intended for adult usage.

Three coats of a commercially-available polyvinyl acetate latex soldunder the trade-name Darex X-56L by the Dewey and Almy Chemical Companywere initially brushed on each bat to provide the priming layer. Theintermediate nitrocellulose layer was obtained by brush application of anitrocellulose lacquer containing about 15 percent by weight of solidscomprising about 71 parts by weight of nitrocellulose resin (RS-30sec.), 22 parts by Weight of dibutyl phthalate and 7 parts by weight ofParaplex RG2 plasticizer dissolved in a solvent mixture comprised of 50parts by weight of ethyl acetate, 15 parts by weight of ethanol andparts by weight of toluene.

The nitrocellulose layer was covered by an enveloping subsequent layerof ethyl cellulose derived by dip application of an ethyl cellulose gellacquer composition. Two' gel lacquer formulations were employed.Formulation A consisted of in the neighborhood of 21-24 percent byweight of 'solids'comprised of 97.5 parts by Weight of a medium ethoxylvalue ethyl cellulose having a viscosity of about 100 centipoises,similar to that which is obtainable under the tradename Ethocel, 100cps. med. from The Dow Chemical Company and 2.5 parts by weight ofParaplex RG-2 plasticizer dissolved in a solvent mixture comprised of 55parts by weight of xylene, 20 parts by weight of Apco Thinner and 25parts by weight of Dowanol 8. Formulation B consisted of about 30.5percent by weight of solids comprised of 70 parts by weight of Ethocel,100 cps. med. and 30 parts by weight of Paraplex RG-Z dissolved in thesame solvent mixture employed for formulation A. Each of the bats wasdip coated, without any occurrence or formation of bubbles, in the gellacquer while the latter was being maintained at a temperature betweenand C.' Pertinent data with regard to the applied multicomponent coatingsystem is given in the following table.

Composite coating applied to baseball bats Little League Adult BatsBats.

Length Range of Bats-inches 29 to 32 34 to 35 Average Weight of EachBatgrams. 672 932 Average Weight of Polyvinyl Acetate Latex Layergrams27 32 Average Weight of N itroeellulose Layer-grams 5 6 Average Weightof Hard Lacquer Top Coat-grams 2 2 Average Weight of Neoprene GripCoatgrams 1 1. 3

- Gel Lacquer Formulation A 1 Coat 20oats 1 Coat 2Coats No. or BatsCoated 12 12 3 3 Average Weight of Ethyl Cellulose Layer-grams 62 91 73116 Gel Lacquer Formulation 13" lCoat 2Coats 1Coat 2Coats No. of BatsCoated 12 12 3 3 Average Weight of Ethyl Cellulose Layer-grams 49 62 128As is indicated by the table, each of the bats was given a light hardtop coat of scuff and dirt-resisting nitrocellulose lacquer which wassprayed over the ethyl cellulose layer of the composite coating. Also,each of the bat handles was provided with a friction grip by paintingthem with a neoprene paint.

All of the coated bats were exceptionally durable and resistant tobreakage. appreciable difference in the hitting reaction or effect ofthe bats on pitched or hand-hit baseballs was discernible, particularlywith respect to. any increased tendency to cause pitched balls to befouled ofi when struck or to be propelled greater or lesser distancesthan when hit by conventional uncoated bats. In addition, the. coatedbats produced a similar sound effect as conventional bats whenever aball was hit with them.

Forty-five (45) of the Little League bats which had been coated weredistributed among teams in the Little League organization in Midland,Michigan, for use during the 1955 sandlot baseball season. For purposes.of comparison, one-hundred-eight (108) conventional uncoated bats ofthe same type were distributed to the same teams on a proportional basiswith the coated, breakage-resisting bats. Equal and representative useof both types of bats in actual play was attempted to be obtained. Atthe end of the 1955 season 78 (or 72.2 percent) of the uncoated batswere broken by the competitors on the Little League teams while only one(or 2.2 percent) of the coated bats was broken in the. course of theseason. The considerable reduction in the incidence of breakage of thecoated bats is outstandingly evident. Similar excellent results wereobtainedwith the coated adult baseball bats.

Analogous advantage and benefit can also be obtained by coating sucharticles as bowling pins and hockey sticks in a manner similar to theforegoing.

Since certain changes and modifications can be readily entered into inthe practice of the present invention without substantially departingfrom its intended spirit and scope, it is to be fully understood thatall the foregoing description and specification be interpreted andconstrued as being merely illustrative of certain of the preferredembodiments of the invention which in no sense or manner is to beunderstood as being limited or restricted thereby excepting as set forthand defined in the appended claims.

What is claimed is: p

1. Method for protectivelycoating wooden surfaces and All other thingsbeing equal, no.

articles to provide them with an increased resistance to breakage whichcomprises first applying a layer of polyvinyl acetate latex to the barewooden surface; then applying a nitrocellulose layer over the polyvinylacetate layer;

and subsequently applying an ethyl cellulose layer over i the polyvinylacetate and nitrocellulose layers by dip application of an ethylcellulose gel lacquer formulation.

gel lacquer formulation from which the subsequently appliedethylcellulose layer is derived is formulated with an ethyl cellulosehaving an ethoxyl content between about '45 and 46.5 percent by weightand a viscosity between about 10 and 200 centipoises, as determined in a5 percent by weight solution thereof in an :20 mixture, by volume, oftoluene and ethanol.

6. The method of claim 4 wherein the ethyl cellulose has a viscositybetween about 50 and centipoises.

7. The method of claim 2and includingthe additional step of covering thesubsequent ethyl cellulose layer with a thin scuff and dirt-resistingtop coat of a hard finish lacquer coating'material. f

8. A breakage-resisting wooden article having a composite,multicomponent, protective coating on its surface comprise ofsequentially superimposed layers of first polyvinyl acetate; thennitrocellulose; and finally ethyl cellulo se.

9. A breakage-resisting wooden article having a composite,multicomponent, protective coating on its surface comprised ofsequentially superimposed layers of first polyvinyl acetate; thennitrocellulose, and finally a layer of ethyl cellulose having athickness of at least about 5 mils.

10. A coated article in accordance with claim 9 wherein the thickness ofthe ethyl cellulose layer is between about 15 and 50 mils.

11. A coated article in accordance with claim 9 wherein the relativeweight proportions of the polyvinyl acetate:

nitrocellulosezethyl cellulose layers over any given area isapproximately in the ratio of 5:1:10-25, respectively, on a dry-weightbasis. Q

12. A coated article in accordance with claim 9 and including anadditional thin top coat over the ethyl cellulose layer of a sculf anddirt-resisting hard finish lacquer coating material. I

13. A coated baseball bat in accordance with claim 9 having anadditional coating of a friction-providing material on its grippingsurface.

References Cited in the file of this patent UNITED STATES PATENTSl,950,662 Dreyfus Mar. 13, 1934 2,101,714 Keeney. Dec. 7, 1937 2,357,458Clough' Sept. 5, 1944 2,586,446 Stockburger Feb. 19, 1952 2,674,544Gibbons Apr. 6, 1954 FOREIGN PATENTS 562,098 Great Britain June 19, 1944

1. A METHOD FOR PROTECTIVELY COATING WOODEN SURFACES ANDD ARTICLES TOPROVIDE THEM WITH AN INCREASED RESISTANCE TOO BREAKAGE WHICH COMPRISESFIRST APPLYING A LAYER OF POLYVINYL ACETATE LATEX TO THE BARE WOODENSURFACE; THEN APPLY-